1. Technical Field
The present invention relates generally to cellular wireless communication networks; and more particularly to packetized voice communications in such a cellular wireless communication network.
2. Related Art
Wireless networks are well known. Cellular wireless networks support wireless communication services in many populated areas of the world. Satellite wireless networks are known to support wireless communication services across most surface areas of the Earth. While wireless networks were initially constructed to service voice circuit-switched voice communications, they are now called upon to support packet-switched data communications as well.
The transmission of data communications within a wireless network places different demands on networks than does the transmission of voice communications. Voice communications require a sustained bandwidth with minimum signal-to-noise ratio (SNR) and continuity requirements. Data communications, on the other hand, typically are latency tolerant but have higher total throughput requirements. Conventional circuit-switched wireless networks were designed to support the well-known voice communication requirements. Thus, wireless networks (as well as conventional circuit switched telephone networks) have been adapted to service data communications, with such adaptation providing mixed results. Thus, future wired and wireless networks will likely be fully packet switched.
Packet switched data networks, e.g., the Internet, were originally constructed to service only data communications. However, these networks have been adapted to service packetized voice communications as well, e.g., Voice Over Internet Protocol (VOIP) telephony. VOIP telephony is fully packet switched, with each VOIP packet including a digitized voice payload. Packet switched networks, which were designed to service data communications and not voice communications, often do not satisfy the requirements of VOIP telephony. Thus, safeguards must be set in place in the network infrastructure to guarantee the minimum sustained bandwidth and continuity requirements of VOIP telephony. These safeguards have been substantially identified for wired networks but not for wireless networks.
With the advent of fully packet-switched wireless networks, VOIP telephony must also be adapted for use in such wireless networks. However, the operational limitations of wireless networks differ significantly from those of wired networks. In servicing a VOIP telephony call, sufficient bandwidth must be allocated and the bandwidth allocation must be serviced with a maximum latency. Wireless networks are generally predictable and can be operated to meet these constraints. However, the uncertainty and constantly changing nature of wireless links often compromises not only the bandwidth requirement but also the maximum latency requirements. These problems are compounded with VOIP telephony because control of the VOIP telephone call is controlled at a relatively high level on the ISO protocol stack.
A particular wireless link between a base station and mobile station varies in quality such that it will support differing data rates at differing times. As a mobile station moves farther away from the base station, the data rate supported by the wireless link will decrease. Further, as wireless interference increases, the data rate supported by the wireless link also decreases. Currently, VOIP telephony supports a fixed data rate for the pendency of a serviced VOIP call. Thus, VOIP telephony calls are not as easily serviced as are conventional circuit switched calls.
Because base station must service a plurality of mobile stations, each base station must judiciously allocate its available bandwidth to a plurality of wireless links. The fixed data rate requirement of VOIP calls may not allow the base station to flexibly manage the requirements of all serviced mobile terminals.
Further, wireless link may be noisy, VOIP telephony packets may be corrupted on their transmission across the wireless links, both on the forward wireless links and the reverse wireless links. VOIP telephony operation fails to address such noisy/erroneous operations. Thus, VOIP calls serviced across the wireless link may include errors that produce only noise when converted to an analog equivalent.
Moreover, VOIP telephony provides no flexibility in managing resources during quite periods. All telephony calls include quiet periods in which no party is speaking. During these quiet periods, VOIP calls carry data at the same rate as during active periods. The transmission of data during these quiet periods consumes wireless link bandwidth but produces no benefits.
Thus, it would therefore be desirable to control packet switched telephony calls, e.g., VOIP calls, so that the wireless link may be more flexibly managed.